An existing axial flow fan includes a plurality of blades along the circumferential surface of a cylindrical boss, and forces a fluid to move by the blades being rotated by rotary force provided to the boss. In the axial flow fan, the fluid present between the blades collides against the surfaces of the blades by rotation of the blades. At each surface against which the fluid collides, the pressure increases and pushes out and moves the fluid in the direction of the rotation axis about which the blades rotate.
In such an axial flow fan, to achieve a decrease in noise and an increase in efficiency, there is an example in which a backward-tilted blade that is tilted toward downstream relative to the flowflow direction of the fluid in a blade cross-section, in a radial direction, passing through the rotation axis of the blade, is used. In addition, there is an example in which an outer circumference reflexed portion (winglet) is formed in the neighborhood of the outer circumferential edge of a blade so as to be reflexed toward upstream relative to the flow direction of the fluid (see Patent Literature 1).